Re: [Boost-users] Needs advices on design ( mpl or processor )

Subject: Re: [Boost-users] Needs advices on design ( mpl or processor )
From: Allan Nielsen (a_at_[hidden])
Date: 2012-01-06 17:19:31

My problem is not to calculate the actually size, but move the
calculation from the instantiation into the definition of the library.

On Fri, Jan 6, 2012 at 11:04 PM, Nevin Liber <nevin_at_[hidden]> wrote:
> On 6 January 2012 13:26, Larry Evans <cppljevans_at_[hidden]> wrote:
>
>> So, IIUC, you want (as the name compressed_enums suggests) want to
>> sum the sizes of each enum,
>
> Assuming size is the number of unique values in a given enum, you want
> to sum the ceiling of log2 of the size of each enum to determine how
> many bits you need.
> <http://www.boost.org/doc/libs/1_48_0/libs/integer/doc/html/boost_integer/log2.html>
> can help with this (although it computes floor(log2(n))). Â Note: to
> get an even denser packing where different enums can share the same
> bit, remove "ceiling of" from the previous sentence.
>
> Example: Â if the first enum has 4 distinct values and the second enum
> has 8 distinct values, you need to be about to store 4x8=32 distinct
> combinations. Â ceil(log2(4)) + ceil(log2(8)) == 2 + 3 == 5 bits.
> --
>  Nevin ":-)" Liber  <mailto:nevin_at_[hidden]>  [phone]
> _______________________________________________
> Boost-users mailing list
> Boost-users_at_[hidden]
> http://lists.boost.org/mailman/listinfo.cgi/boost-users